I understand "activist" in this context to be something closer to "interpreting the law in some unusual way nobody could have thought of when they wrote it", as opposed to "using a clause to the letter of the law in an unambiguous way and any reasonable person would agree that that was the intent of the law to begin with" which is the case with ÓLG.
I think his detractors just don't like that he shit on their parade, so instead of addressing that issue they're making this absurd argument that he used a clause of law that had never been used before and ubsetting that status quo is somehow bad, while conveniently forgetting that that unprecedented clause was invoked in the midddle of an unprecedented financial crisis.
Really? The best description? By that definition pretty much anyone in politics is an activist.
I think it's much more accurate to describe ÓLG as a literal constitutionalist.
He read the letter of the law and followed its mandate.
He's undoubtedly upset the established older. I'm just objecting to how that gets framed, which you can just as easily frame his actions as "nobody serving as president before him had actually read the constitution" as "he's using unprecedented powers as president".